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use futex instead of pthread cond variable for schedule

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This commit is contained in:
Kent Overstreet 2018-02-05 00:13:40 -05:00
parent 7c29c458db
commit 27c0b6fbc5
3 changed files with 11 additions and 21 deletions
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5
include/linux/sched.h
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@ -74,11 +74,8 @@ struct task_struct {
int (*thread_fn)(void *);
void *thread_data;
pthread_mutex_t lock;
pthread_cond_t wait;
atomic_t usage;
volatile long state;
int state;
/* kthread: */
unsigned long kthread_flags;

2
linux/kthread.c
View File

@ -68,8 +68,6 @@ struct task_struct *kthread_create(int (*thread_fn)(void *data),
p->thread_fn = thread_fn;
p->thread_data = thread_data;
p->state = TASK_UNINTERRUPTIBLE;
pthread_mutex_init(&p->lock, NULL);
pthread_cond_init(&p->wait, NULL);
atomic_set(&p->usage, 1);
init_completion(&p->exited);

25
linux/sched.c
View File

@ -1,4 +1,5 @@
#include <linux/futex.h>
#include <string.h>
#include <sys/mman.h>
@ -6,6 +7,7 @@
#include <linux/printk.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/timer.h>
__thread struct task_struct *current;
@ -19,28 +21,23 @@ void __put_task_struct(struct task_struct *t)
/* returns true if process was woken up, false if it was already running */
int wake_up_process(struct task_struct *p)
{
int ret;
int ret = p->state != TASK_RUNNING;
pthread_mutex_lock(&p->lock);
ret = p->state != TASK_RUNNING;
p->state = TASK_RUNNING;
pthread_cond_signal(&p->wait);
pthread_mutex_unlock(&p->lock);
futex(&p->state, FUTEX_WAKE|FUTEX_PRIVATE_FLAG,
INT_MAX, NULL, NULL, 0);
return ret;
}
void schedule(void)
{
int v;
rcu_quiescent_state();
pthread_mutex_lock(&current->lock);
while (current->state != TASK_RUNNING)
pthread_cond_wait(&current->wait, &current->lock);
pthread_mutex_unlock(&current->lock);
while ((v = current->state) != TASK_RUNNING)
futex(&current->state, FUTEX_WAIT|FUTEX_PRIVATE_FLAG,
v, NULL, NULL, 0);
}
static void process_timeout(unsigned long __data)
@ -169,8 +166,6 @@ static void sched_init(void)
memset(p, 0, sizeof(*p));
p->state = TASK_RUNNING;
pthread_mutex_init(&p->lock, NULL);
pthread_cond_init(&p->wait, NULL);
atomic_set(&p->usage, 1);
init_completion(&p->exited);